Method for producing low phosphorus steel in 80t quantum electric furnace

Abstract

This invention discloses a method for producing low-phosphorus steel using a quantum electric furnace. The production steps are as follows: The furnace body angle is zeroed. Preheated scrap steel and molten iron are added to the furnace, and electrode submerged arc heating is initiated. Simultaneously, 3-6 kg / t of lime and 1-3 kg / t of dolomite are added. After heating for 1-2 minutes, the furnace body is tilted towards the tapping side, and oxygen blowing with the oxygen-reducing lance is initiated. Lime is added in batches during oxygen blowing. After the oxidation reaction in the furnace is completed, the furnace body is tilted towards the slag-discharging side to remove the oxidized slag. After slag discharge, the furnace body is tilted towards the tapping side, and 0-5 kg / t of lime is added. After smelting for another 2-6 minutes, the temperature and composition of the molten steel meet the requirements, and the tapping operation begins. This invention achieves efficient dephosphorization by adjusting the tilting direction of the furnace body at different smelting stages. High-basicity slag is retained in the furnace during the early stages of smelting, while phosphorus-rich slag is discharged during and after the dephosphorization period, thus preventing phosphorus reversion in the molten steel as the temperature rises in the later stages of smelting. This results in stable and efficient production of steel with a phosphorus content <0.010%.

Description

Technical Field

[0001] This invention relates to the field of steelmaking and smelting, specifically to a method for producing low-phosphorus steel using an 80t quantum electric furnace. Background Technology

[0002] Compared to traditional electric arc furnaces, quantum electric arc furnaces offer advantages such as efficient preheating of scrap steel, flat-pool smelting, and siphon tapping. However, when smelting high-quality steel, they still face the daunting task of dephosphorization. Regarding efficient dephosphorization in electric arc furnace smelting, especially for producing ultra-low phosphorus steel (phosphorus content <0.010%), traditional processes are still employed, primarily relying on large slag volumes and low molten steel temperatures. In some electric arc furnaces, slag flows out from the tapping side during smelting, but this is passively caused by a large slag volume. The slag cannot be completely removed; in the later stages of smelting, once the molten steel temperature is high, phosphorus from the slag will return to the molten steel through a reverse reaction, resulting in high phosphorus content in the steel. This necessitates the addition of large amounts of lime and other materials for further dephosphorization.

[0003] Existing electric arc furnace (EAF) dephosphorization methods limit the production of low-cost, fast-paced, high-temperature, and low-oxidizing molten steel. Currently, there are no innovative technologies for efficient dephosphorization using quantum electric arc furnaces. Achieving efficient dephosphorization using quantum electric arc furnaces through relevant production innovations will create broader opportunities for their application in low-energy, fast-paced, and high-quality production. Summary of the Invention

[0004] To address the aforementioned problems, this invention discloses a method for producing low-phosphorus steel using an 80t quantum electric furnace, the specific technical solution of which is as follows: A method for producing low-phosphorus steel using a quantum electric furnace includes the following steps: Step 1) Zero the angle of the quantum electric furnace body, add preheated scrap steel to 500-800℃ and molten iron at a mass ratio of 0-40% into the furnace to start electrode submerged arc heating. After the heating starts, add 3-6 kg / t of lime and 2-5 kg / t of dolomite. Step 2) After heating and smelting for 1-2 minutes until the slag foam index reaches >60, tilt the furnace body towards the tapping side at an angle of -0.5° to -2° to prevent oxidized slag from flowing out from the tapping side. Begin using the two oxygen lances on the tapping and slag tapping sides at a speed of 17-28 minutes. 3 / h·t oxygen blowing, during which lime is added in 2 to 3 batches, with an interval of 1 to 3 minutes between each addition; Step 3) After smelting for 8-15 minutes, wait for the oxidation reaction of silicon, manganese and phosphorus elements in the furnace to end and the temperature of the molten steel in the furnace to reach above 1500℃. Tilt the furnace body towards the slag discharge side and adjust the angle of the furnace body. At the same time, stop the oxygen lance near the slag discharge side and leave only the oxygen lance near the steel discharge side to blow oxygen. Discharge the oxidized slag in the furnace from the furnace door at the slag discharge side. Step 4) After smelting for another 2-5 minutes, 50-70 kg / t of oxide slag flows out from the slag outlet. The phosphorus content in the steel is within the range of phosphorus composition for the steel grade. The furnace body is tilted towards the tapping side with an angle of -1° to 0°. 0-5 kg / t of lime is added and smelted for another 2-6 minutes to raise the temperature of the molten steel while ensuring that the phosphorus content in the molten steel does not rise back. After the smelting end point, the temperature of the molten steel reaches >1620℃, the phosphorus content is <0.010%, and other components meet the requirements, the tapping operation begins.

[0005] Furthermore, in step 1), the furnace body angle is zeroed out, and the furnace body angle is between -0.5° and 0°.

[0006] Furthermore, in step 1), the initial phosphorus content of the molten steel is 0.05% to 0.08%.

[0007] Furthermore, in step 2), the amount of lime added and the amount of oxygen blown are adjusted according to the target phosphorus content required at the end point of steel tapping, as follows: When the final phosphorus content is ≤0.003%, the lime addition amount is 35-42 kg / t, and the oxygen blowing amount is 25-28 m³ / t. 3 / h·t; When the final phosphorus content is ≤0.005% and 0.003% < the endpoint, the lime addition rate is 35-26 kg / t, and the oxygen blowing rate is 21-26 m³ / t. 3 / h·t; When the final phosphorus content is 0.005% < 0.008%, the lime addition rate is 22–26 kg / t, and the oxygen blowing rate is 19–23 m³ / t. 3 / h·t; When the final phosphorus content is ≤0.010% and the lime content is 0.008%, the lime addition rate is 19-23 kg / t, and the oxygen blowing rate is 17-22 m³ / t. 3 / h·t.

[0008] Furthermore, in step 3), the furnace tilt angle is set according to the target phosphorus content as follows: When the final phosphorus content is ≤0.003%, the furnace angle is 4°~5°; When the final phosphorus content is 0.003% < 0.005%, the furnace angle is 3° to 4°. When the final phosphorus content is 0.005% < 0.008%, the furnace angle is 1.5° to 3°. When the final phosphorus content is 0.008% < 0.010%, the furnace angle is 0.5° to 2°.

[0009] The beneficial effects of this invention are: First, this invention controls the amount of oxidized slag in the furnace at different stages, so that the furnace contains low-phosphorus oxidized slag when the steel is dephosphorized and the phosphorus content in the steel is <0.010%. Then, the high-phosphorus-enriched oxidized slag is discharged from the furnace in time, realizing efficient dephosphorization of the steel during the smelting process. In the later stage of smelting, it avoids the reverse reaction of phosphorus pentoxide in the slag caused by the increase of steel temperature (the steel temperature reaches >1620℃, or even >1650℃), which would cause the phosphorus content in the steel to increase again.

[0010] Secondly, this invention, while using low lime content, achieves stable control and minimal fluctuations in phosphorus content and temperature in the molten steel at the electric furnace smelting endpoint. This avoids the need for prolonged smelting time due to increased phosphorus content in the molten steel during the later stages of smelting, requiring additional lime addition and temperature reduction. This reduces production energy consumption.

[0011] Third, this invention improves the production pace, with smelting time <30 minutes, temperature reaching above 1620℃, phosphorus recovery in the later stage of smelting <0.002%, ensuring that the phosphorus content of the molten steel is <0.010%. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the structure of the quantum electric furnace of the present invention. Detailed Implementation

[0013] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0014] Combination Figure 1 The specific method of the present invention is as follows: Step 1) Zero the angle of the quantum electric furnace body, add preheated scrap steel to 500-800℃ and molten iron at a mass ratio of 0-40% into the furnace to start electrode submerged arc heating. The initial phosphorus content of the molten steel is 0.05%-0.08%. After the heating starts, add 3-6 kg / t of lime and 2-5 kg / t of dolomite.

[0015] Step 2) After heating and smelting for 1-2 minutes until the slag foam index reaches >60, tilt the furnace body towards the tapping side at an angle of -0.5° to -2° to prevent oxidized slag from flowing out from the tapping side. Begin using the two oxygen lances on the tapping and slag tapping sides at a speed of 17-28 minutes. 3 Oxygen blowing is carried out at a rate of / h·t. During oxygen blowing, lime is added in 2 to 3 batches, with an interval of 1 to 3 minutes between each addition.

[0016] The amount of lime added and the amount of oxygen blown are adjusted according to the target phosphorus content required at the end of the steel tapping process, as shown in Table 1: Table 1

[0017] Step 3) After smelting for 8-15 minutes, wait for the oxidation reaction of silicon, manganese and phosphorus elements in the furnace to end and the temperature of the molten steel in the furnace to reach above 1500℃. Tilt the furnace body towards the slag discharge side and adjust the angle of the furnace body. At the same time, stop the oxygen lance near the slag discharge side and leave only the oxygen lance near the steel discharge side to blow oxygen. Discharge the oxidized slag in the furnace from the furnace door at the slag discharge side.

[0018] The furnace tilt angle is set according to the target phosphorus content, as shown in Table 2: Table 2

[0019] Step 4) After smelting for another 2-5 minutes, 50-70 kg / t of oxide slag flows out from the slag outlet. The phosphorus content in the steel is within the range of phosphorus composition for the steel grade. The furnace body is tilted towards the tapping side with an angle of -1° to 0°. 0-5 kg / t of lime is added and smelted for another 2-6 minutes to raise the temperature of the molten steel while ensuring that the phosphorus content in the molten steel does not rise back. After the smelting end point, the temperature of the molten steel reaches >1620℃, the phosphorus content is <0.010%, and other components meet the requirements, the tapping operation begins.

[0020] The following are two specific embodiments of the application of this invention: Example 1: Production of 20CrMnTi steel with phosphorus content <0.010% using the process of the present invention. The quantum electric furnace body tilt angle is set to 0°. Scrap steel and molten iron, preheated to approximately 600°C, are added to the furnace at a 25% iron-to-metal ratio to initiate electrode submerged arc heating. Simultaneously, 4 kg / t of lime and 5 kg / t of dolomite are added. After 2 minutes of heating and smelting, the slag foam index reaches above 60. The furnace body is then tilted -2° towards the tapping side to prevent low-temperature, low-phosphorus slag from flowing out of the furnace. Oxygen blowing is then initiated using two oxygen lances on the tapping and slag-tapping sides, with an oxygen flow rate of 18–20 m³ / h. 3 During oxygen blowing, lime is added in two batches, 11 kg / t per batch, to form slag for oxidation and dephosphorization. After 13 minutes of smelting, once the oxidation reaction in the furnace is complete and the phosphorus content of the molten steel reaches 0.012%, the furnace body is tilted 1.5° towards the slag outlet. Simultaneously, the oxygen lances near the slag outlet are stopped, leaving only the lances near the tapping side to continue blowing oxygen, continuously discharging the oxidized slag from the furnace door near the slag outlet. After 3 minutes of smelting, the amount of discharged oxidized slag reaches 55 kg / t. Once the oxidized slag no longer flows from the slag outlet, the furnace body is tilted -0.5° towards the tapping side, 3 kg / t of lime is added, and smelting continues for another 3 minutes, reaching a molten steel temperature of 1635℃. w (P) = 0.008%, which meets the process requirements, so the steel tapping operation can proceed.

[0021] Example 2: Production of 55 steel with phosphorus content <0.006% using the process of the present invention The quantum electric furnace body is tilted at -0.3°. Scrap steel and molten iron (25% iron-to-metal ratio) are added to the furnace at a preheated temperature of approximately 600°C to initiate electrode submerged arc heating. Simultaneously, 6 kg / t of lime and 3 kg / t of dolomite are added. After 2 minutes of heating and smelting, when the slag foam index reaches above 60, the furnace body is tilted -2° towards the tapping side. Oxygen blowing is then initiated using two oxygen lances on the tapping and slag-tapping sides, with an oxygen flow rate of 24–26 m³ / h. 3 During oxygen blowing, lime is added in three batches, 10 kg / t per batch. After 11 minutes of smelting, once the oxidation reaction in the furnace is complete and the phosphorus content of the molten steel reaches 0.005%, the furnace body is tilted 4° towards the slag discharge side. Simultaneously, oxygen blowing is stopped at the oxygen lance near the slag discharge side, leaving only the oxygen lance near the tapping side to blow oxygen. Oxidized slag is continuously discharged from the furnace door near the slag discharge point. After 5 minutes of smelting, when the amount of discharged oxidized slag reaches 65 kg / t and no longer flows from the slag outlet, the furnace body is tilted -1° towards the tapping side, and 5 kg / t of lime is added. Smelting continues for another 6 minutes. Temperature sampling is performed; the molten steel temperature is 1625℃. w (P) = 0.004%, which meets the process requirements, so the steel tapping operation can proceed.

[0022] The process conditions not specified in the above production methods can be referred to conventional techniques in the field. Referring to the quantum electric furnace slag retention and flow production method of the present invention, by controlling the furnace body tilt angle at different smelting stages, all the initial slag is retained in the furnace, and then the dephosphorized oxidized slag enriched with phosphorus is discharged in time, which can achieve low slag volume smelting, and the molten steel in the furnace at high temperature with no phosphorus return at the end of the smelting, resulting in efficient, stable and smooth production.

[0023] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0024] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for producing low-phosphorus steel using a quantum electric furnace, characterized in that, Includes the following steps: Step 1) Zero the angle of the quantum electric furnace body, add preheated scrap steel to 500-800℃ and molten iron at a mass ratio of 0-40% into the furnace to start electrode submerged arc heating. After the heating starts, add 3-6 kg / t of lime and 2-5 kg / t of dolomite. Step 2) After heating and smelting for 1-2 minutes until the slag foam index reaches >60, tilt the furnace body towards the tapping side at an angle of -0.5° to -2° to prevent oxidized slag from flowing out from the tapping side. Begin using the two oxygen lances on the tapping and slag tapping sides at a speed of 17-28 minutes. 3 / h·t oxygen blowing, during which lime is added in 2 to 3 batches, with an interval of 1 to 3 minutes between each addition; Step 3) After smelting for 8-15 minutes, wait for the oxidation reaction of silicon, manganese and phosphorus elements in the furnace to end and the temperature of the molten steel in the furnace to reach above 1500℃. Tilt the furnace body towards the slag discharge side and adjust the angle of the furnace body. At the same time, stop the oxygen lance near the slag discharge side and leave only the oxygen lance near the steel discharge side to blow oxygen. Discharge the oxidized slag in the furnace from the furnace door at the slag discharge side. Step 4) After smelting for another 2-5 minutes, 50-70 kg / t of oxide slag flows out from the slag outlet. The phosphorus content in the steel is within the range of phosphorus composition for the steel grade. The furnace body is tilted towards the tapping side with an angle of -1° to 0°. 0-5 kg / t of lime is added and smelted for another 2-6 minutes to raise the temperature of the molten steel while ensuring that the phosphorus content in the molten steel does not rise back. After the smelting end point, the temperature of the molten steel reaches >1620℃, the phosphorus content is <0.010%, and other components meet the requirements, the tapping operation begins.

2. The production method for dephosphorization using quantum electric furnace slag retention according to claim 1, characterized in that, In step 1), the furnace body angle is zeroed out, and the furnace body angle is between -0.5° and 0°.

3. The production method for dephosphorization using a quantum electric furnace with slag retention according to claim 1, characterized in that, In step 1), the initial phosphorus content of the molten steel is 0.05% to 0.08%.

4. The production method for dephosphorization using a quantum electric furnace slag retention system according to claim 1, characterized in that, In step 2), the amount of lime added and the amount of oxygen blown are adjusted according to the target phosphorus content required at the end point of steel tapping, as follows: When the final phosphorus content is ≤0.003%, the lime addition amount is 35-42 kg / t, and the oxygen blowing amount is 25-28 m³ / t. 3 / h·t; When the final phosphorus content is ≤0.005% and 0.003% < the endpoint, the lime addition rate is 35-26 kg / t, and the oxygen blowing rate is 21-26 m³ / t. 3 / h·t; When the final phosphorus content is 0.005% < 0.008%, the lime addition rate is 22–26 kg / t, and the oxygen blowing rate is 19–23 m³ / t. 3 / h·t; When the final phosphorus content is ≤0.010% and the lime content is 0.008%, the lime addition rate is 19-23 kg / t, and the oxygen blowing rate is 17-22 m³ / t. 3 / h·t.

5. The production method for dephosphorization using quantum electric furnace slag retention according to claim 1, characterized in that, In step 3), the furnace tilt angle is set according to the target phosphorus content as follows: When the final phosphorus content is ≤0.003%, the furnace angle is 4°~5°; When the final phosphorus content is 0.003% < 0.005%, the furnace angle is 3° to 4°. When the final phosphorus content is 0.005% < 0.008%, the furnace angle is 1.5° to 3°. When the final phosphorus content is 0.008% < 0.010%, the furnace angle is 0.5° to 2°.

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